RFC: Allow interfaces to implement other interfaces

src/execution/__tests__/union-interface-test.js

@@ -49,23 +49,46 @@ const NamedType = new GraphQLInterfaceType({
   },
 });
 
+const LifeType = new GraphQLInterfaceType({
+  name: 'Life',
+  fields: () => ({
+    progeny: { type: GraphQLList(LifeType) },
+  }),
+});
+
+const MammalType = new GraphQLInterfaceType({
+  name: 'Mammal',
+  interfaces: [LifeType],
+  fields: () => ({
+    progeny: { type: GraphQLList(MammalType) },
+    mother: { type: MammalType },
+    father: { type: MammalType },
+  }),
+});
+
 const DogType = new GraphQLObjectType({
   name: 'Dog',
-  interfaces: [NamedType],
-  fields: {
+  interfaces: [MammalType, LifeType, NamedType],
+  fields: () => ({
     name: { type: GraphQLString },
     barks: { type: GraphQLBoolean },
-  },
+    progeny: { type: GraphQLList(DogType) },
+    mother: { type: DogType },
+    father: { type: DogType },
+  }),
   isTypeOf: value => value instanceof Dog,
 });
 
 const CatType = new GraphQLObjectType({
   name: 'Cat',
-  interfaces: [NamedType],
-  fields: {
+  interfaces: [MammalType, LifeType, NamedType],
+  fields: () => ({
     name: { type: GraphQLString },
     meows: { type: GraphQLBoolean },
-  },
+    progeny: { type: GraphQLList(CatType) },
+    mother: { type: CatType },
+    father: { type: CatType },
+  }),
   isTypeOf: value => value instanceof Cat,
 });
 
@@ -84,12 +107,15 @@ const PetType = new GraphQLUnionType({
 
 const PersonType = new GraphQLObjectType({
   name: 'Person',
-  interfaces: [NamedType],
-  fields: {
+  interfaces: [NamedType, MammalType, LifeType],
+  fields: () => ({
     name: { type: GraphQLString },
     pets: { type: GraphQLList(PetType) },
     friends: { type: GraphQLList(NamedType) },
-  },
+    progeny: { type: GraphQLList(PersonType) },
+    mother: { type: PersonType },
+    father: { type: PersonType },
+  }),
   isTypeOf: value => value instanceof Person,
 });
 
@@ -116,6 +142,15 @@ describe('Execute: Union and intersection types', () => {
           enumValues { name }
           inputFields { name }
         }
+        Mammal: __type(name: "Mammal") {
+          kind
+          name
+          fields { name }
+          interfaces { name }
+          possibleTypes { name }
+          enumValues { name }
+          inputFields { name }
+        }
         Pet: __type(name: "Pet") {
           kind
           name
@@ -134,7 +169,16 @@ describe('Execute: Union and intersection types', () => {
           kind: 'INTERFACE',
           name: 'Named',
           fields: [{ name: 'name' }],
-          interfaces: null,
+          interfaces: [],
+          possibleTypes: [{ name: 'Person' }, { name: 'Dog' }, { name: 'Cat' }],
+          enumValues: null,
+          inputFields: null,
+        },
+        Mammal: {
+          kind: 'INTERFACE',
+          name: 'Mammal',
+          fields: [{ name: 'progeny' }, { name: 'mother' }, { name: 'father' }],
+          interfaces: [{ name: 'Life' }],
           possibleTypes: [{ name: 'Person' }, { name: 'Dog' }, { name: 'Cat' }],
           enumValues: null,
           inputFields: null,

src/language/__tests__/schema-kitchen-sink.graphql

@@ -51,6 +51,12 @@ extend interface Bar {
 
 extend interface Bar @onInterface
 
+interface Baz implements Bar {
+  one: Type
+  two(argument: InputType!): Type
+  four(argument: String = "string"): String
+}
+
 union Feed = Story | Article | Advert
 
 union AnnotatedUnion @onUnion = A | B

src/language/__tests__/schema-parser-test.js

@@ -183,7 +183,7 @@ extend type Hello {
     expect(printJson(doc)).to.equal(printJson(expected));
   });
 
-  it('Extension without fields', () => {
+  it('Object extension without fields', () => {
     const body = 'extend type Hello implements Greeting';
     const doc = parse(body);
     const expected = {
@@ -203,7 +203,27 @@ extend type Hello {
     expect(printJson(doc)).to.equal(printJson(expected));
   });
 
-  it('Extension without fields followed by extension', () => {
+  it('Interface extension without fields', () => {
+    const body = 'extend interface Hello implements Greeting';
+    const doc = parse(body);
+    const expected = {
+      kind: 'Document',
+      definitions: [
+        {
+          kind: 'InterfaceTypeExtension',
+          name: nameNode('Hello', { start: 17, end: 22 }),
+          interfaces: [typeNode('Greeting', { start: 34, end: 42 })],
+          directives: [],
+          fields: [],
+          loc: { start: 0, end: 42 },
+        },
+      ],
+      loc: { start: 0, end: 42 },
+    };
+    expect(printJson(doc)).to.equal(printJson(expected));
+  });
+
+  it('Object extension without fields followed by extension', () => {
     const body = `
       extend type Hello implements Greeting
 
@@ -235,14 +255,53 @@ extend type Hello {
     expect(printJson(doc)).to.equal(printJson(expected));
   });
 
-  it('Extension without anything throws', () => {
+  it('Interface extension without fields followed by extension', () => {
+    const body = `
+      extend interface Hello implements Greeting
+
+      extend interface Hello implements SecondGreeting
+    `;
+    const doc = parse(body);
+    const expected = {
+      kind: 'Document',
+      definitions: [
+        {
+          kind: 'InterfaceTypeExtension',
+          name: nameNode('Hello', { start: 24, end: 29 }),
+          interfaces: [typeNode('Greeting', { start: 41, end: 49 })],
+          directives: [],
+          fields: [],
+          loc: { start: 7, end: 49 },
+        },
+        {
+          kind: 'InterfaceTypeExtension',
+          name: nameNode('Hello', { start: 74, end: 79 }),
+          interfaces: [typeNode('SecondGreeting', { start: 91, end: 105 })],
+          directives: [],
+          fields: [],
+          loc: { start: 57, end: 105 },
+        },
+      ],
+      loc: { start: 0, end: 110 },
+    };
+    expect(printJson(doc)).to.equal(printJson(expected));
+  });
+
+  it('Object extension without anything throws', () => {
     expectSyntaxError('extend type Hello', 'Unexpected <EOF>', {
       line: 1,
       column: 18,
     });
   });
 
-  it('Extension do not include descriptions', () => {
+  it('Interface extension without anything throws', () => {
+    expectSyntaxError('extend interface Hello', 'Unexpected <EOF>', {
+      line: 1,
+      column: 23,
+    });
+  });
+
+  it('Object extension do not include descriptions', () => {
     expectSyntaxError(
       `
       "Description"
@@ -263,6 +322,27 @@ extend type Hello {
     );
   });
 
+  it('Interface extension do not include descriptions', () => {
+    expectSyntaxError(
+      `
+      "Description"
+      extend interface Hello {
+        world: String
+      }`,
+      'Unexpected Name "extend"',
+      { line: 3, column: 7 },
+    );
+
+    expectSyntaxError(
+      `
+      extend "Description" interface Hello {
+        world: String
+      }`,
+      'Unexpected String "Description"',
+      { line: 2, column: 14 },
+    );
+  });
+
   it('Simple non-null type', () => {
     const body = `
 type Hello {
@@ -322,6 +402,32 @@ type Hello {
     expect(printJson(doc)).to.equal(printJson(expected));
   });
 
+  it('Simple interface inheriting interface', () => {
+    const body = 'interface Hello implements World { field: String }';
+    const doc = parse(body);
+    const expected = {
+      kind: 'Document',
+      definitions: [
+        {
+          kind: 'InterfaceTypeDefinition',
+          name: nameNode('Hello', { start: 10, end: 15 }),
+          interfaces: [typeNode('World', { start: 27, end: 32 })],
+          directives: [],
+          fields: [
+            fieldNode(
+              nameNode('field', { start: 35, end: 40 }),
+              typeNode('String', { start: 42, end: 48 }),
+              { start: 35, end: 48 },
+            ),
+          ],
+          loc: { start: 0, end: 50 },
+        },
+      ],
+      loc: { start: 0, end: 50 },
+    };
+    expect(printJson(doc)).to.equal(printJson(expected));
+  });
+
   it('Simple type inheriting multiple interfaces', () => {
     const body = 'type Hello implements Wo & rld { field: String }';
     const doc = parse(body);
@@ -351,6 +457,35 @@ type Hello {
     expect(printJson(doc)).to.equal(printJson(expected));
   });
 
+  it('Simple interface inheriting multiple interfaces', () => {
+    const body = 'interface Hello implements Wo & rld { field: String }';
+    const doc = parse(body);
+    const expected = {
+      kind: 'Document',
+      definitions: [
+        {
+          kind: 'InterfaceTypeDefinition',
+          name: nameNode('Hello', { start: 10, end: 15 }),
+          interfaces: [
+            typeNode('Wo', { start: 27, end: 29 }),
+            typeNode('rld', { start: 32, end: 35 }),
+          ],
+          directives: [],
+          fields: [
+            fieldNode(
+              nameNode('field', { start: 38, end: 43 }),
+              typeNode('String', { start: 45, end: 51 }),
+              { start: 38, end: 51 },
+            ),
+          ],
+          loc: { start: 0, end: 53 },
+        },
+      ],
+      loc: { start: 0, end: 53 },
+    };
+    expect(printJson(doc)).to.equal(printJson(expected));
+  });
+
   it('Simple type inheriting multiple interfaces with leading ampersand', () => {
     const body = 'type Hello implements & Wo & rld { field: String }';
     const doc = parse(body);
@@ -380,6 +515,35 @@ type Hello {
     expect(printJson(doc)).to.equal(printJson(expected));
   });
 
+  it('Simple interface inheriting multiple interfaces with leading ampersand', () => {
+    const body = 'interface Hello implements & Wo & rld { field: String }';
+    const doc = parse(body);
+    const expected = {
+      kind: 'Document',
+      definitions: [
+        {
+          kind: 'InterfaceTypeDefinition',
+          name: nameNode('Hello', { start: 10, end: 15 }),
+          interfaces: [
+            typeNode('Wo', { start: 29, end: 31 }),
+            typeNode('rld', { start: 34, end: 37 }),
+          ],
+          directives: [],
+          fields: [
+            fieldNode(
+              nameNode('field', { start: 40, end: 45 }),
+              typeNode('String', { start: 47, end: 53 }),
+              { start: 40, end: 53 },
+            ),
+          ],
+          loc: { start: 0, end: 55 },
+        },
+      ],
+      loc: { start: 0, end: 55 },
+    };
+    expect(printJson(doc)).to.equal(printJson(expected));
+  });
+
   it('Single value enum', () => {
     const body = 'enum Hello { WORLD }';
     const doc = parse(body);
@@ -433,6 +597,7 @@ interface Hello {
         {
           kind: 'InterfaceTypeDefinition',
           name: nameNode('Hello', { start: 11, end: 16 }),
+          interfaces: [],
           directives: [],
           fields: [
             fieldNode(

src/language/__tests__/schema-printer-test.js

@@ -95,6 +95,12 @@ describe('Printer: SDL document', () => {
 
       extend interface Bar @onInterface
 
+      interface Baz implements Bar {
+        one: Type
+        two(argument: InputType!): Type
+        four(argument: String = "string"): String
+      }
+
       union Feed = Story | Article | Advert
 
       union AnnotatedUnion @onUnion = A | B

src/language/ast.js

@@ -458,6 +458,7 @@ export type InterfaceTypeDefinitionNode = {
   +loc?: Location,
   +description?: StringValueNode,
   +name: NameNode,
+  +interfaces?: $ReadOnlyArray<NamedTypeNode>,
   +directives?: $ReadOnlyArray<DirectiveNode>,
   +fields?: $ReadOnlyArray<FieldDefinitionNode>,
 };
@@ -527,6 +528,7 @@ export type InterfaceTypeExtensionNode = {
   +kind: 'InterfaceTypeExtension',
   +loc?: Location,
   +name: NameNode,
+  +interfaces?: $ReadOnlyArray<NamedTypeNode>,
   +directives?: $ReadOnlyArray<DirectiveNode>,
   +fields?: $ReadOnlyArray<FieldDefinitionNode>,
 };